ad hoc hypothesis

An ad hoc hypothesis is one created to explain away facts that seem to refute
ones belief or theory. Ad hoc hypotheses are common in paranormal research and in the work of pseudoscientists. For example, ESP
researchers have been known to blame the hostile thoughts of onlookers for unconsciously
influencing pointer readings on sensitive instruments. The hostile vibes, they say, made
it impossible for them to duplicate a positive ESP experiment. Being able to duplicate an
experiment is essential to confirming its validity. Of course, if this objection is taken
seriously, then no experiment on ESP can ever fail. Whatever the results, one can always
say they were caused by paranormal psychic forces, either the ones being tested or others
not being tested.

Martin Gardner reports on this type of ad hoc hypothesizing reaching a ludicrous peak
with paraphysicist Helmut Schmidt who put cockroaches in a box where they could give
themselves electric shocks. One would assume that cockroaches do not like to be shocked
and would give themselves shocks at a chance rate or less, if cockroaches can learn from
experience. The cockroaches gave themselves more electric shocks than predicted by chance.
Schmidt concluded that "because he hated cockroaches, maybe it was his pk that
influenced the randomizer!" (Gardner, p. 59)

Ad hoc hypotheses are common in defense of the pseudoscientific theory known as biorhythm theory. For example, there are very many people who do
not fit the predicted patterns of biorhythm theory. Rather than accept this fact as
refuting evidence of the theory, a new category of people is created: the
arrhythmic. In
short, whenever the theory does not seem to work, the contrary evidence is systematically
discounted. Advocates of biorhythm theory claimed that the theory could be used to
accurately predict the sex of unborn children. However, W. S. Bainbridge, a professor of
sociology at the University of Washington, demonstrated that the chance of predicting the
sex of an unborn child using biorhythms was 50/50, the same as flipping a coin. An
expert in biorhythms tried unsuccessfully to predict accurately the sexes of the children
in Bainbridge's study based on Bainbridge's data. The expert's spouse suggested to
Bainbridge an interesting ad hoc hypothesis, namely, that the cases where the theory was
wrong probably included many homosexuals with indeterminate sex identities!

Astrologers are often fond of using statistical data and analysis to impress us with
the scientific nature of astrology. Of course, a scientific
analysis of the statistical data does not always pan out for the astrologer. In those
cases, the astrologer can make the data fit the astrological paradigm by the ad hoc
hypothesis that those who do not fit the mold have other, unknown influences that
counteract the influence of the dominant planets.

Using ad hoc hypotheses is not limited to pseudoscientists. Another type of ad hoc
hypothesis occurs in science when a new scientific theory is proposed which conflicts with
an established theory and which lacks an essential explanatory mechanism. An ad hoc
hypothesis is proposed to explain what the new theory cannot explain. For example, when
Wegener proposed his theory of continental drift he could not explain how continents move.
It was suggested that gravity was the force behind the movement of continents, though
there was no scientific evidence for this notion. In fact, scientists could and did show
that gravity was too weak a force to account for the movement of continents. Alexis du
Toit, a defender of Wegener's theory, argued for radioactive melting of the ocean floor at
continental borders as the mechanism by which continents might move. Stephen Jay Gould
noted that "this ad hoc hypothesis added no increment of plausibility to Wegener's
speculation." (Gould, p. 160)

Finally, rejecting explanations that require belief in occult, supernatural or
paranormal forces in favor of simpler and more plausible explanations is called applying Occam's razor. It is not the same as ad hoc hypothesizing. For
example, let's say I catch you stealing a watch from a shop. You say you did not steal it.
I ask you to empty your pockets. You agree and pull out a watch. I say, "Aha!, I was
right. You stole the watch." You reply that you did not steal the watch, but you
admit that it was not in your pocket when we went into the store. I ask you to explain how
the watch got into your pocket and you say that you used telekinesis: you used your
thoughts to transport the watch out of a glass case into your pocket. I ask you to repeat
the act with another watch and you say "ok." Try as you will, however, you
cannot make a watch magically appear in your pocket. You say that there is too much
pressure on you to perform or that there are too many bad vibes in the air for you to work
your powers. You have offered an ad hoc hypothesis to explain away what looks like a good
refutation of your claim. My hypothesis that the watch is in your pocket because you stole
it, is not an ad hoc hypothesis. I have chosen to believe a plausible explanation rather
than an implausible one. Likewise, given the choice between believing that my headache
went away of its own accord or that it went away because some nurse waved her hands over
my hand while chanting a mantra, I will opt for the former every time.

It is always more reasonable to apply Occam's razor than to offer speculative ad hoc
hypotheses just to maintain the possibility of something supernatural or paranormal.